About Light Waves?

Question

Can anyone tell me whether light waves travel and cause vibrations of molecules like sound waves cause vibrations of molecules parallel to the direction of wave propagation or any transverse waves which cause molecules to move at right angles to the direction of wave propagation. And if light causes vibration of molecules, why is it that we see light but we cannot hear it nor we can see sound.

I also want to know why we do not see other electromagnetic waves. Light is one among them and travels at the same speed like tem, yet we can see light but not the other electromagnetic waves. how come this? Y can't our eyes see radio waves or gamma rays???

Answer 1

Light waves are not the vibration of molecules or any physical entity. They are electric and magnetic fields interacting as described by Maxwell's equations. These equations show that a time-varying magnetic field creates an electric field, and conversely, a time-varying electric field creates a magnetic field. The equations can be solved to derive the case in which the electric fields and magnetic fields vary in such a way that each creates the other in a self-sustaining interaction. When this is done, the result is an equation of a travelling wave that moves at the speed of 1/sqrt(e0*m0) in free space. e0 and m0 are electrical properties of space called permitivity and permeability. it turns out that the speed of light in a vacuum is exactly that value. This result was the convincing proof that light was electromagnetic waves.

Answer 2

Light waves (and all other electromagnetic waves) travel as photons (tiny packets of pure energy without mass) at the speed of light. The photons can travel through a perfect vacuum (unlike sound waves that need gas molecules to propagate). The photons can be created when the electrons orbiting an atom fall from energetic orbits to smaller rest orbits releasing excess energy. On the other hand, photons can be captured by electrons and kicked up into more energetic orbits. You can see light (but not infra red or ultra violet light) because tiny cones on your retina contain pigments that are sensitive to the three primary colors (red blue and yellow) which are activated when struck by the photons with just the right wavelengths. Colorblind people lack one or more of the pigments and perceive colors differently. Light waves can not be heard because they are not strong enough to move the ear drum. In fact strong light waves would burn tissue (like using a magnifying glass to burn a leaf).

Answer 3

Second part of the question, since I'm not sure what you're asking in the first part, sound is caused by molecules of air bumping into each other en masse, causing a pressure wave that eventually reaches your ear. What your eardrum does is move back and forth based on the pressure changes. Light can energize an atom/molecule to higher energy levels, but this does not necessarily translate as increased motion of the atom/molecule, it could just result in higher energy levels of the electrons within the atom. However, with that said, if you blasted a pocket of air with a LOT of light energy in a fraction of a second, it would heat up, causing a pressure pulse in the air which you could hear as a "pop".

Answer 4

In light the vibration of both the electric and magnetic field is perpendicular to the direction of motion not like sound wave. The highest frequency we can hear is 20 Khz much below the Gigahertz of light. Light cause vibrations of molecules. Micro-wave heating is an application of this. Micro-waves being low frequency light so to speak

Answer 5

I don't think that light waves move, but I am not totally sure. I want to be an astronomer so I probably need to know this. Sounds are vibrations and the molecules are moving so fasr we can't see the sound. But light is vibrations but are slower so therefore we can see them. If you need better examples or if you still don't under stand email me at [e-mail]. I hope I was a little help.

Answer 6

Light, unlike sound, does not need a material to travel through. When light does travel through a material (e.g. glass) it interacts not by transmitting mechanical vibrations but by being captured and re-emitted by electrons.

Light that is absorbed by a material turns into heat. The frequency of light is too high to produce mechanical vibrations in a material. Visible light ranges from about 400 to 750 Tera-Hz (trillion cycles per second); atomic resonances are typically more than an order of magnitude less, maybe 20THz or so. All of which is way beyond the frequency range we can hear (20 to 20,000 or so Hz).

We see light because it causes chemical changes in receptor cells in our eyes, which cause neurons to fire. These cells are not sensitive to sound.

Answer 7

Light waves are electromagnetic radiation or waves that propogate at the speed of light (c). Some forms are visible to the human eye; others are not. Each form (or color) is characterized by its frequency (f) (or wavelength (l), since f*l=c).

The motion that you are trying to tie in analogously to sound is found in disturbances of electric field and magnetic field strength.

Visible and UV light perturbs electrons which are acting more wave-like rather than particle-like in this context. This causes excitation of the electron rather than vibration of the chemical bonds. Microwave light causes molecular rotation and IR light causes bond rotation. None of these is necessarily strongly tied into molecular *translational* motion (but can be, to make life interesting/miserable...).

So, the reason why we see light is because our photo-detectors generally respond to excited (and relaxing) electrons (or breaking chemical bonds). The light doesn't have sufficient energy to trigger our audio-sensors.

We "hear" sound through detecting the motion of a large number (quadrillions or more) of molecules moving (usually back and forth, but not necessarily). In particular, we detect the vibration of a membrane. Sounds doesn't have the right kind of energy to trigger our visual sensors.

Kind of a handwavy answer (there are alot of exceptions and/or special cases which are sort of cheating, i.e., you can make an electronic device that translates sounds into colors and/or light levels into sounds to "hear light" or "see sounds" without the benefit of drugs... :-) ), but I hope that points you in the right direction.

Answer 8

No, unlike sound light does not propagate through vibrations in matter. In the late 1800's and early 1900's physicists assumed that light propagated through a medium called ether. However, they never able to experimentally prove that ether existed. This is what lead to the discovery of special relativity. As far as I know today there is still no experimental evidence to suggest that an ether exist. I personally believe it does not.

Answer 9

the q depends on whether or not light is a wave or a particle

Answer 10

Sorry, not answerable in a couple of sentences. Study science and all will become clear.